Quantum dot self consistent electronic structure and the Coulomb blockade

TL;DR

This paper uses density functional theory to analyze the electronic structure and Coulomb blockade phenomena in semiconductor quantum dots, revealing shell effects and their impact on conductance and experimental deviations.

Contribution

It introduces a self-consistent approach to compute quantum dot properties without capacitance parameters, incorporating shell structure and disorder effects.

Findings

Shell structure causes modulation of Coulomb oscillation peaks

Dot capacitances are influenced by shell effects

Results explain deviations from random matrix theory predictions

Abstract

We employ density functional theory to calculate the self consistent electronic structure, free energy and linear source-drain conductance of a lateral semiconductor quantum dot patterned via surface gates on the 2DEG formed at the interface of a $GaAs-AlGaAs$ heterostructure. The Schr\"{o}dinger equation is reduced from 3D to multi-component 2D and solved via an eigenfunction expansion in the dot. This permits the solution of the electronic structure for dot electron number $N \sim 100$. We present details of our derivation of the total dot-lead-gates interacting free energy in terms of the electronic structure results, which is free of capacitance parameters. Statistical properties of the dot level spacings and connection coefficients to the leads are computed in the presence of varying degrees of order in the donor layer. Based on the self-consistently computed free energy as a function of gate voltages, $V_i$, and N, we modify the semi-classical expression for the tunneling conductance as a function of gate voltage through the dot in the linear source-drain, Coulomb blockade regime. Among the many results presented, we demonstrate the existence of a shell structure in the dot levels which (a) results in envelope modulation of Coulomb oscillation peak heights, (b) which influences the dot capacitances and should be observable in terms of variations in the activation energy for conductance in a Coulomb oscillation minimum, and (c) which possibly contributes to departure of recent experimental results from the predictions of random matrix theory.